Pacific Northwest National Laboratory (PNNL) researchers have developed a self-healing cement for geothermal wellbore applications.
The self-healing cement is said to outperform conventional concrete as it uses a flexible polymer to repair fractured surfaces and fill cracks, helping reduce mechanical failure risks.
The PNNL study was undertaken by lead chemist Carlos Fernandez and his team, in collaboration with Brookhaven National Laboratory’s (BNL) Simerjeet Gill.
Cement used in geothermal wells is known to crack under pressure and in high-temperature environments where drilling is involved.
The team’s objective was to see how its self-healing cement would hold up when tested against conventional cement in these extreme heat conditions.
As per tests conducted at PNNL and BNL’s National Synchroton Light Source II, the team found that the self-healing cement technology could eliminate the need to remove, repair and replace cracked cement wells.
The researchers also tested their self-healing cement’s strength and reactions to mechanical stress and conducted analyses of surface area, chemical composition, and surface topography.
The tests confirmed that the self-healing cement is a significant alternative to conventional cement because it is flexible and autonomously heals cracks.
The cement’s flexibility is attributed to ‘chemically soft’ or flexible bonding between the atoms in the polymer and cement.
This soft bonding allows large deformations that can be contained within the cement without breaking the bonds.
The polymer also adds 60% to 70% more elasticity to the cement, reducing fractures in the cement, notes Fernandez.
On their own, polymers are large, chain-like molecules that work to hold substances together. When added to cement, polymers add flexibility to brittle material and keep cracks from spreading quickly.
It works by detaching and migrating to the crack, and attaches back to fill the crack.
According to the researchers, there was an 87% reduction in crack size when the polymer was added to the concrete.
Fernandez contends that the polymer-cement combination could amount to $3.4 billion a year in savings for infrastructures like dams, nuclear waste facilities, and skyscrapers.
Conventional cement costs 5 cents per pound while polymer-cement is about 30 to 35 cents per pound.
It nevertheless extends the life of concrete-based structures by 30 to 50 years, and this is where the cost-savings benefits reign supreme, says Fernandez.
Image and content: PNNL